Introduction

Did you know the large intestine of a human is about 1.5m long? This is about a fifth of the total digestive system of a human!¹

The large intestine is crucial for absorbing water from the food and liquid we take in. It also removes any waste material which is not needed by the body. The material left at the end of the digestion process is called faeces, and it’s stored in the rectum (the last portion of the large intestine). The large intestine has a vast blood supply from several arteries and veins. This is essential to supply oxygen to the length of the intestine where digestion occurs.¹

Definition of ischaemic proctitis 

Ischaemic proctitis is a potentially serious condition where not enough blood flows to the last part of the digestive tract. Ischaemia refers to reduced blood flow and oxygen being delivered to body parts. Proctitis is inflammation (as indicated by the -itis) of the lining of the last part of the bowel – the rectum. 

Importance of understanding its causes, symptoms and treatment

Ischaemic proctitis is a potentially serious, life-threatening condition. It can have severe consequences, which will be further discussed later in this article. Therefore, understanding how to identify the condition and its causes will potentially help you to modify lifestyle factors to reduce the risk. 

Causes of ischaemic proctitis

The causes of ischaemic proctitis can broadly be divided into occlusive and non-occlusive causes. Occlusive causes are caused by a blockage in the blood vessels supplying the bowel, meaning blood and oxygen cannot flow to the rectum. Non-occlusive causes are caused by a reduction in the body’s blood pressure. Whilst blood can still flow to the bowel, its volume is greatly reduced, as the pressure of the blood is lower than usual.

Occlusive

Occlusive ischaemic proctitis is often caused by thromboembolism. This is when a blood clot forms somewhere in the body before travelling and becoming stuck somewhere else. In this case, it becomes stuck in one of the vessels supplying the rectum. Common causes of thromboembolism are: 

• Atrial fibrillation – an irregular heartbeat which increases your risk of forming blood clots
• Myocardial infarction – also known as a heart attack. This can increase your risk of forming a blood clot after a heart attack
• Heart valve disease – if someone has a problem with one of their heart valves, such as a narrowing or not opening properly, a blood clot can form and travel around the body
• Post-surgery – thromboembolisms can form following a surgical operation of a bulging, weakened large vessel in the abdomen² (otherwise known as an abdominal aortic aneurysm)
• Clotting disorders – underlying health conditions which cause blood clots to form easily

Non-occlusive

Non-occlusive ischaemic proctitis is caused by insufficient blood supply to the blood vessels supplying the rectum – either due to a drop in the body’s blood pressure or narrowing of the blood vessels. Non-occlusive ischaemia is often less severe than occlusive ischaemia. Causes of this include: 

• Drop in blood pressure caused by severe infection, severe allergy, heart failure or large blood loss. 
• Diabetes 
• Secondary to radiation treatment 
• Cocaine abuse³
• Long distance running⁴

Symptoms 

Symptoms of this condition vary from case to case. The symptoms largely depend on the severity of the ischaemia in the bowel. Common symptoms are:⁵

• Abdominal pain – Initially located in the left side of the abdomen before becoming more widespread
• Bleeding from the back passage – Bright, fresh blood separate from stool
• Diarrhoea – Stool may be looser than usual 
• High temperature
• Loss of control of the back passage⁶

Diagnosis 

The diagnosis of Ischaemic Proctitis can be difficult, especially at an early stage of the disease. This is because the level of oxygen deprivation of the bowel is still minimal at this point. 

At the beginning of the disease, blood tests can point towards the diagnosis. Elevated levels of lactic acid and white blood cell count have been seen in some patients with the condition.⁷ However, these tests are non-specific, meaning their levels are not raised uniquely in ischaemic colitis and are raised in several other conditions. 

CT scans are probably the most commonly used investigation to diagnose the condition. Although they do not show every case of the condition, they are quick and easy to perform, so they are useful in managing patients with suspected ischaemic colitis. They can often also show alternative diagnoses other than ischaemic colitis, which present with similar symptoms. 

Endoscopy – evaluating the colon using a camera – is the definitive investigation if the diagnosis remains unclear. This test is performed by visualising the last part of the colon using a scope with a camera, which is passed via the back passage. A biopsy (a small sample of tissue from the colon) can be obtained during this and viewed under a microscope.

Treatment options 

Conservative management 

The most common treatment of ischaemic proctitis is conservative, without any medical or surgical treatments. In mild cases, symptoms can often resolve by themselves in 2 – 3 days. 

If an underlying cause of the ischaemic proctitis is suspected, medications may be given to treat this, e.g. treating an irregular heartbeat.

Additional treatments may also be provided. These may include intravenous fluids to treat dehydration. Antibiotics are sometimes given because there is an increased risk of infections in the bowel. 

Surgical management 

In severe cases of the condition, surgery may be the only option. This may be because of irreversible damage to the colon. The surgery will involve removing dead tissue, removing whole parts of the colon which are damaged or repairing holes in the colon. 

Complications 

Unfortunately, there can be some long-term serious complications of ischaemic proctitis: 

• Chronic ischaemic colitis – This is long-term bowel ischaemia and occurs in roughly 20% patients.⁸ Symptoms include bloody diarrhoea, abdominal pain and recurrent infections
• Colonic stricture – Scar tissue forming in the bowel
• Bowel obstruction – If a stricture causes blockage in the bowel, this can be a life-threatening emergency. This is usually managed by surgery
• Perforation – The bowel ischaemia can weaken the walls of the bowel and cause small holes to form. This can cause persistent bleeding and life-threatening infections

Prevention 

As previously discussed, ischaemic proctitis can be hard to identify and therefore sometimes difficult to prevent. However, some risk factors can definitely be optimised to reduce your risk of the condition. These include good hydration (especially during vigorous exercise), reducing dietary cholesterol and quitting smoking. 

The early identification and treatment of conditions which can cause occlusive ischaemic proctitis is also essential. These include atrial fibrillation and heart valve disease. 

Summary

Ischaemic proctitis is a condition in which the last part of the bowel is starved of oxygen and stops functioning as it should. This is potentially life-threatening and can have severe consequences. It has many causes, including uncontrolled atrial fibrillation and heart valve disease. If you notice any of the symptoms described above, please seek urgent medical attention. 

Much of the condition is still poorly understood, including exactly how some risk factors predispose people to ischaemic proctitis. Therefore, more research is required to work out the exact mechanisms involved in the disease process.